package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

@Slf4j
@Component
public class CacheClient {

    private final StringRedisTemplate stringRedisTemplate;

    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }

    public void set(String key, Object value, Long time, TimeUnit timeUnit) {
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value), time, timeUnit);
    }

    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit timeUnit) {
        //设置逻辑过期时间
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(timeUnit.toSeconds(time)));

        //写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));

    }

    public <R,ID> R queryWithLogicalExpire(String keyPrefix , ID id , Class<R> type , Function<ID,R> dbFallback , Long time, TimeUnit timeUnit) {
        //1.从redis查询店铺缓存
        String key =  keyPrefix + id ;
        String json = stringRedisTemplate.opsForValue().get(key);

        //2.判断缓存是否存在
        if (StrUtil.isBlank(json)) {
            //3.存在,直接返回
            return null;
        }

        //4. 命中,需要先把Json反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        JSONObject data = (JSONObject) redisData.getData();
        R r = JSONUtil.toBean(data, type);
        LocalDateTime expireTime = redisData.getExpireTime();

        //5. 判断是否过期
        if(!expireTime.isBefore(LocalDateTime.now())){
            //5.1 未过期,返回店铺信息
            return r;
        }

        //5.2 已过期,进行缓存重建
        //缓存重建
        //6.1 获取互斥锁
        String lockKey = RedisConstants.LOCK_SHOP_KEY + id;
        //6.2 判断获取锁是否成功
        boolean isLock = tryLock(lockKey);
        if (isLock) {
            //6.3 获取锁成功,开启独立线程,开始缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                //重建缓存
                try {
                    R r1 = dbFallback.apply(id);
                    this.setWithLogicalExpire(key,r1,time,timeUnit);

                } catch (Exception e) {
                    throw new RuntimeException(e);
                }finally {
                    //释放锁
                    unlock(lockKey);
                }
            });
        }
        //6.4返回过期的商铺信息

        //4.不存在.根据id查询数据库

        return r;
    }

    public <R,ID> R queryWithThrough(String keyPrefix,ID id,Class<R> type , Function<ID,R> dbFallback ,Long time, TimeUnit timeUnit) {
        //1.从redis查询店铺缓存
        String key =  keyPrefix + id ;
        String json = stringRedisTemplate.opsForValue().get(key);

        //2.判断缓存是否存在
        if (StrUtil.isNotBlank(json)) {
            //3.存在,直接返回
            return JSONUtil.toBean(json, type);
        }

        if (json != null) {
            //返回一个错误信息
            return null;
        }


        //4.不存在.根据id查询数据库
        R r = dbFallback.apply(id);

        //5. 不存在,返回错误
        if (r == null) {
            //将空值写入redis
            stringRedisTemplate.opsForValue().set(key,"",RedisConstants.CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;
        }

        //6.存在,写入redis
        this.set(key,r,time,timeUnit);

        //7.返回
        return r;
    }

    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    private void unlock(String key){
        stringRedisTemplate.delete(key);
    }
}
